This invention relates to bituminous roofing adapted for the waterproofing and sealing of substrate structures and to the method of manufacturing such materials. More particularly, the present invention is in the field of roofing underlayments, having a factory-applied self-adhesive layer on the bottom surface and a thermoplastic modifier such as atactic polypropylene modified bituminous compound on the top surface in order to provide easy and hassle-free field application by roofing personnel.
It is well known to use bituminous compositions for manufacturing waterproofing membranes, generally for roof covering and roofing underlayments. Modified bituminous prepared roofing, also referred to as modified asphalt roofing membrane, is typically manufactured using, as a core, a reinforcement carrier support sheet made of fabric such as polyester, fiberglass, or a combination of both, saturating and coating the front and back sides of the carrier with a modified bituminous coating material based on Atactic Polypropylene (APP), Amorphous Poly Alpha Olefin (APAO), Thermoplastic Polyolefin (TPO), Styrene-Butadiene-Styrene (SBS), Styrene-Ethylene-Butadiene-Styrene (SEBS), synthetic rubber or other asphaltic modifiers, that will enhance the properties of asphalt.
Roofing membranes are used in commercial, industrial and residential applications. Two major classifications of modified bitumen roofing materials, which are used mostly in industrial and commercial applications are (1) cap sheet and (2) base sheet. Shingle roofing materials, however, are used primarily in residential applications, and are exposed to the elements, and hence can be considered as ‘cap’ as well. A cap sheet or shingle membrane can be modified using Atactic Polypropylene (APP), Amorphous Poly Alpha Olefin (APAO), Thermoplastic Polyolefin (TPO), Styrene-Butadiene-Styrene (SBS), Styrene-Ethylene-Butadiene-Styrene (SEBS), synthetic rubber or other asphaltic modifiers, and is generally reinforced with a polyester carrier or a combination of polyester and fiberglass. These sheets can be smooth or granular surfaced and are typically greater than 2.8 mm in thickness. The top surface of the cap sheet is exposed to the elements and hence the name “cap”. A base sheet is typically modified using any of the same modifiers as a cap sheet, but due to economic considerations, is modified using smaller quantities of less expensive polymers such as Atactic Polypropylene (APP) or Styrene-Butadiene-Styrene (SBS). A base sheet is generally reinforced with a fiberglass carrier (which costs significantly lower than polyester) and is smooth surfaced. The thickness of such base sheet typically ranges from 1.0 mm to 2.5 mm depending upon the job specifications. In a typical field installation, a base sheet is first applied to the roof deck using mechanical fasteners, via hot mopping or using cold application techniques. Cap sheets or shingles are applied on top of the base sheets, with the seams of adjacent rolls in offset relation. Most APP-modified bitumen membranes are torch-applied, i.e., by heating the back side of the sheet to melt the compound and using the molten compound to form a heat weld. Most SBS-modified bitumen membranes are set during in-field application in hot mopping asphalt, torch-applied or adhered with cold-process adhesives, as described in U.S. Pat. No. 5,807,911 issued to Wentz, et al., on Sep. 1, 1992. Modified bitumen membranes which do not have factory-applied granule or foil surfacing need some form of field-applied ultraviolet protective coating.
Of the two general types of bituminous sheet materials used for roofing applications, i.e., bitumen-SBS and bitumen-APP materials, the bitumen-SBS products are more elastic, with greater flexibility at low temperatures. APP-based products, however, are more heat-resistant (due to a higher softening point), are more resistant against the effects of the atmosphere (especially ultra-violet rays) and more resistant to foot traffic
The manufacture of bituminous roofing material with multiple layers is well known. For example, U.S. Pat. Nos. 2,893,889; 4,755,409; 4,871,605; and EP Patent No. 903435 disclose membranes comprised of a core and a plurality of different layers of waterproofing material. The '409 patent also discloses a release sheet applied to the one side of the membrane for purposes of protection. Products are in the market which combine the more flexible and elastic bitumen-SBS upper layer with a self-adhesive lower surface. An example of such a product is Plura AD self-adhesive sold by Pluvitec S.p.A., described on the website of the seller at http://www.pluvitec.com. Application of a primer is recommended when using this material in order to ensure adherence of the self-adhesive layer to a substrate, and the use of added heat, i.e., by a torch, is also recommended.
Roofing underlayment materials are used in roofing systems such as modified bituminous roofing membranes as well as shingles, tiles, slates, cedar and metal roofing. Some underlayments such as asbestos fiber roofing felts were used during the early part of the 20th century but are no longer used due to health hazards associated with asbestos fibers. The most commonly used underlayment is asphalt-saturated roofing felt, commonly known as No. 15, No. 30 or No. 50 felt. These have been in use for a very long time and are the least expensive form of underlayment available. Roofing felt is made from a base sheet made of paper coated with filler-modified asphalt and as such is very inexpensive. Several roofing companies produce such materials. The main objective of using felt is to provide a protective barrier on the deck when applying roofing membranes by means of hop mopping, torching or self-adhesive applications. Several building code bodies such as Miami Metro Dade County authority dictates the use of slip sheet in all roofing applications under its jurisdiction. This is to ensure that the roof deck such as plywood is not damaged during ‘roof tear off’ when replacing the roof.
Roofing felts have been in short supply periodically and due to supply-demand factors, the price of felt has continued to rise over the years. Interestingly, felts have several limitations. It is well known that roofs undergo significant expansion and contraction as they heat and cool throughout the day. Because of such thermal cycling, felts experience shrinkage when exposed to the elements and exhibit deterioration in a relatively short period of time. Moreover felts are not watertight when roofing nails or staples are driven through them, making it necessary to cover the felt underlayment with the next course of roofing material immediately upon installation of the felt to the deck. These limitations, coupled with frequent shortage of felt underlayments, have forced roofers and contractors to search for alternate materials. Sheets which are sold as membranes in roll form may be cut into smaller sections to form shingles for use on roofs with greater slope. Shingles are typically nailed into place, and are most commonly used in residential roofing.
Another category of roofing membranes are “underlayments”, which are widely used in residential applications, and may also be designed for use in regions with colder climates, where ice-dam protection is required. Underlayments, commonly utilized under shingle roofing material, metal roofing panels or tile roofing, provide waterproofing characteristics and are typically reinforced with fiberglass. However, there are a few products in the market place that have no carrier such that these consist of simply a coating of self-adhesive compound on a polyolefinic film. Polystick P made by Polyglass USA, Grace Ice & Water Shield and Grace Vycor Ultra manufactured by W. R. Grace & Company are examples of such materials. These non-carrier based underlayments are typically very soft and are ideally suited for use in areas of roofs such as perimeters, hips, valleys, etc. where ice dam formation may occur during winter.
Roofing underlayments are applied to the underlying substrates using a variety of methods. One such technique is using mechanical fasteners, which is a slow and cumbersome process. During installation of a roof, roofing underlayments are attached to the wood deck by ‘mechanically fastening’ using roofing nails or staples. Based on the roof specifications, another course of material such as No. 90 felt is applied on top of the No. 15 or No. 30 felt, usually via hot asphalt mopping. Upon installation of such underlayment, metallic panels may be mechanically fastenedon the top surface
Hot mopping, in which drums or cartons of hot asphalt are used, although poses a reduced risk of fire versus torch application, still poses an operational problem. Hot-mopping application, which requires a fair amount of labor, especially in larger projects, also results in waste cartons with chemical residue. These dirty cartons must be disposed of properly, for example, in landfills, and become unsafe for the environment. In addition, disposal of the waste materials become costly and labor-intensive. Alternatively, hot asphalt is directly pumped to the roof from the ground using a hose. Whereas this method eliminates the aforementioned problems associated with disposal of cartons, etc., it poses other problems in that it is very difficult and dangerous to pump hot asphalt to the roof level, especially in the case of high-rise buildings. Furthermore, the end result of the above-described in field applications is also not successful each and every time. Moreover these products are based on application methods that pose environmental and operational hazards during the roof installation.
There are several non-felt, modified bitumen based materials that are designed to be used under metal roofing. All of these materials are based on SBS modified bituminous compound. Examples of such products are ‘Tile and Metal Underlayment’ manufactured by Tamko Roofing Company of Joplin, Missouri and ‘Grace Vycor Ultra’ manufactured by W. R. Grace and Company of Cambridge, Mass. It is essential to note that metal generates excess heat and therefore necessitates the use of an underlayment that can withstand high temperature. Also granular surfaced products, whether APP or SBS based, are not recommended since the mineral surface can cause abrasion on the metal. This poses severe problems for the installer of such roofing underlayments in that these products are modified with styrene-butadiene-styrene (SBS) compound, which is soft and flows at temperatures above 110 degrees Celsius. Hence it is necessary to develop a product that is very easy to install as well as durable enough to offer high heat resistance and a non-abrasive surface on the exposed side. Such material must also be economical, thereby making use of commercial roofing membranes as underlayment materials cost prohibitive.
There is, therefore, a need to provide a self-adhering metal underlayment material, which reduces labor and installation costs, reduces VOCs and emissions from hot mop applications and eliminates the need for use of nails. The present invention permits a more simplified, safer and economical roof installation without compromising structural integrity and lap sealing capabilities. It also offers a suitable means to dramatically reduce field labor by offering a ‘dual compound’ product, which eliminates the numerous undesirable aspects of the prior art.
One object of the present invention is to provide membranes with well-embedded, non-abrasive, high temperature resistant fabric surface that is highly durable. Fabric surfacing is applied to the upper surface of the top asphaltic coating layer to impart weathering, high temperature resistant characteristics and skid resistant characteristics.
It is still another object of the present invention to provide a unique APP modified bitumen compound on the top surface that is very “hard”. When metal panels heat up during the daytime, especially in summer, heat is transferred to the underlayment below. This transfer of heat softens the modified compound, more profoundly in the case of SBS, which is by far the preferred modifier in most existing underlayments, and causes the compound to flow. Use of a hard APP compound alleviates this problem. APP modified compound utilized on the top surface offers plastomeric characteristics to the bitumen and makes the membrane very hard and imparts improved flow resistance at high temperatures. A typical softening point temperature of APP modified compound is in excess of 150 degrees Celsius, whereas that of conventional SBS modified compound is approximately 120 degrees Celsius.
The present invention deals with metal underlayment sheet based on dual compound technology whereby an APP compound is applied on the top surface of the reinforcement and a self-adhesive compound is applied on the bottom surface of the reinforcement. Dual compound technology allows enhanced adhesion of the tacky self-adhesive material to the roof deck because the self-adhesive compound is applied in the factory under controlled conditions rather than in the field where contamination and variation in application techniques are considerably more of a problem.
This invention specifically deals with applying a “dual compound” to the reinforcement carrier sheet—a compound based on Atactic Polypropylene (APP) or Amorphous Poly Alpha Olefin (APAO) or Thermoplastic Polyolefin (TPO) on the top surface, and a separate heat-and-pressure-activated adhesive compound to the bottom surface of the reinforcement carrier sheet. APP modified bitumen compound by itself does not possess any adhesive properties to directly adhere to any substrate. Similarly, self-adhesive compounds have “very poor” weathering characteristics, thereby undergoing premature degradation with exposure to the elements. Dual compound combines the best of an APP and a self-adhesive compound. The advantage of a “dual” compound is the ability to add a “true” roofing compound such as an APP modified bitumen on the top (weathering) surface and a self-adhesive compound on the bottom surface. The thickness of such cap membranes is between 1.0 mm and 3.0 mm. Typical weight of a one square roll (1 roofing square equals 107.6 square feet) is between 60 pounds and 80 pounds, depending upon thickness of the membrane. Such membranes may be reinforced with a polyester, fiberglass or polyester/fiberglass combination mat. Generally, fiberglass is used as a carrier in tile underlayment sheets due to their low cost. A release liner, typically made of polypropylene, polyethylene or polyester, of thickness ranging from 40 to 80 microns, and treated with a silicone adhesive on one side (the side that comes in contact with compound), is applied to the self-adhesive compound to prevent sticking of adjacent sections of the roofing material and to the packaging when the finished membrane is stored and transported in the form of rolls.
The present invention involves roof underlayment sheets having a top layer of an APP modified bituminous compound, whose composition utilizes bitumen (asphalt), APP plastomeric modifiers and fillers, and a bottom layer of a self-adhesive compound, whose composition utilizes bitumen (asphalt), elastomeric modifiers, tackifying resins, and fillers. A typical APP compound may contain 5% to 25% of polypropylene modifiers, 8% to 70% of filler such as limestone or talc, and remaining portions of asphalt. In order to achieve fire ratings as classified by Underwriters' Laboratories (UL), special fire retardant additives may be used as filler. A typical self-adhesive compound may contain 3% to 10% of Styrene-butadiene-styrene modifiers, 0% to 5% of Styrene-isoprene-styrene modifiers, 6% to 25% of hydrocarbon tackifying resins, 8% to 40% of filler such as limestone, talc, fly ash, volcanic ash, graphite, carbon black, silica or china clay, and remaining portions of asphalt.
The inventive membrane has a carrier that supports a dual compound modified asphalt, namely, an APP modified asphaltic compound which is positioned on top of the carrier sheet, and a self-adhesive modified asphaltic compound which is positioned below the carrier sheet. The adherent material serves to affix the metal underlayment material to the base sheet or roof deck. In order to provide adhesion and a watertight seal, a self-adhesive compound that is compatible with the modified bituminous coating layer must be utilized. The factory-applied self-adhesive compound provides an adhesive layer to the underlayment sheet having sufficient surface tack (“quick grab”), as well as adequate strength for use in adhering the underlayment sheet to an underlying surface such as roofing felt or deck.
In the case of metal underlayments, a suitable surfacing agent such as a non-woven fabric material is applied to the upper surface to achieve non-skid properties in addition to high temperature resistance. If the top surface is too smooth, it may not provide the necessary skid resistance for the installer of the product. Hence it is essential to have a coarser surface on the exposed side. Fabrics have a rough texture that provides a measure of skid resistance. Fabrics are used in a variety of applications including roofing membranes, furniture, etc. and are usually made of polyester, polypropylene or polyethylene. Apex Inc. of Georgia, Spun Indo Jaya of Indonesia and Texbond of Italy are sources of such lightweight fabrics. During manufacture of fabrics, surfactants are added to aid in processing the material. Such additives can interfere with lamination of the fabric to the modified bituminous compound during manufacture, and hence it is important that the fabric materials have minimum level of surfactant. When selecting fabric for this lamination to the top side of the APP modified bituminous compound, it is critical to note that the fabric must not be too thick that it may not get sufficiently laminated to the modified bituminous compound. For the manufacture of the inventive metal underlayment material, fabric based on polypropylene is chosen. Polypropylene fabrics are lightweight, readily available and are economical. PP fabric selected for this lamination was of unit weight ranging from 22 to 30 grams/meter2 in order to facilitate ease of lamination to the modified bituminous compound. Whereas the color of the fabric does not affect skid resistance, lighter color fabrics possess higher reflectivity and thereby maintain the underlayment surface cooler. Metal underlayments surfaced with darker colored fabrics absorb more heat and hence the APP compound gets softer. It is therefore preferable to use lighter color fabrics for metal underlayment applications.
Another suitable surfacing agent that can be applied to the upper surface is film material. Such film material must have treatment on the exposed surface to achieve non-skid properties. If the top surface is too smooth, it may not provide the necessary skid resistance for the installer of the product. Hence it is essential to provide a non-skid treatment on the exposed side. Such film must also exhibit high temperature resistance and resistance to the harmful effects of sun's ultraviolet rays. Polyolefinic films are used in a variety of applications including roofing membranes, food packaging, grocery bags, etc. and are usually made of polypropylene or polyethylene. PCL Packaging of Massachusetts, Sipa of Italy, and Cartenplast of Italy are sources of such films. During manufacture of these films, anti-skid additives can be incorporated to aid in providing skid resistance properties. When selecting film for laminating to the upper side of the modified bituminous compound, it is critical to note that the film must not be too thick that it may not get sufficiently embedded in the modified bituminous compound. For the manufacture of the inventive metal underlayment material, film based on polyethylene is chosen. Further high density polyethylene (HDPE) is preferred for this application. Polyethylene films are readily available and are economical. HDPE film selected for this lamination was of thickness ranging from 2 mil (50 microns) to 4 mil (100 microns) in order to facilitate ease of lamination to the modified bituminous compound. However the preferred thickness is 2.8 mil (70 micron). Whereas the color of the film does not affect skid resistance, lighter color fabrics possess higher reflectivity and thereby maintain the underlayment surface cooler. Metal underlayments surfaced with darker colored fabrics absorb more heat and hence the modified bituminous compound gets softer. It is therefore preferable to use lighter color films for metal underlayment applications. The HDPE film of the present invention is treated with an anti-skid coating on the upper surface. Such coating is usually in the form of straight lines or a geometric pattern and consists of adhesives such as Ethyl Vinyl Acetate (EVA), Amorphous Poly Alpha Olefin (APAO), PolyAmide or Pressure Sensitive Adhesives (PSA). For this invention, an EVA adhesive called Jowatherm Hot Melt Adhesive from Jowat Corporation, North Carolina was chosen.
Metal underlayment of the present invention is also suited for use as an underlayment in roofing tile applications. However non-woven fabrics have low strength and as such may be unable to resist movement of tiles on rooftops (such as groups of tiles stored during assembly or simply the tiles on steeper roofs). Whereas non-woven polypropylene fabric is used as the top layer in laminate in the case of metal underlayment, a stitch-bonded polyester fabric is the preferred choice for the top layer of the laminate for the metal underlayment when the same will be employed as a roofing tile underlayment. Stitch-bonded polyester is lightweight as well but possesses very high tear strength due to its process of manufacture and unique construction. Tie-Tex International of South Carolina is a leading manufacturer of such material. When metal underlayment of the present invention is manufactured using stitch-bonded polyester on the upper surface, the resultant material is well suited for use as a roofing tile underlayment as well.